Reafler, U.S. patent application Ser. No. 116,426, describes a flexible and stretchable sheet material that is capable of being stretched to conform to a three dimensional substrate to form a protective and decorative coating thereon. The sheet material is comprised of a thin flexible support having adhered thereto a protective and decorative layer such as a paint layer comprising a colorant incorporated in a film-forming binder. The sheet material can also comprise an adhesion-promoting tie-layer between the support sheet and the protective and decorative layer, and a clear topcoat. An adhesive backcoat can also be provided on the side of the support opposite the protective and decorative layer.
In addition to a colorant and a binder the paint layer can contain reflective particles, of which aluminum flakes are a leading example. The reflective flakes provide an aesthetically pleasing effect because of both sparkle and geometric metamerism or "flop". Flop results because of the flake reflections that are lighter than white pigment close to the specular reflection angle and which fall off rapidly away from the specular reflection angle to very much darker than white pigment. Particularly when the flakes are oriented substantially parallel to the film surface, the high degree of flop provides lightness variations which emphasize the lines and contours of the decorated three-dimensional substrate.
The sheet material of the Reafler application is applied to a three-dimensional substrate by thermoforming, usually with vacuum and/or air pressure. The sheet is softened by heating to a substantially plastic state, and plastically stretched to an extended state depending on the shape of the substrate.
The sheet material is thus brought into conforming association with at least one surface of the substrate and is securely bonded to the substrate to form thereon a smooth and wrinkle-free protective and decorative coating.
A potential problem with dried paint layers that contain reflective metal flakes, is that when stretched during a thermoforming operation, they may exhibit a loss in gloss. Although the applicants do not wish to be bound by theoretical considerations, they believe that a major cause of the loss of gloss in such a coating is a roughening of the coating surface resulting from the lack of plastic flow of the metal flakes, in contrast to the plastic flow of the surrounding polymeric vehicle during thermoforming. This results in surface protuberances, more pronounced when several metal flakes are positioned one beneath the other.
The present invention provides an improvement in a paint composition containing metal flakes and in articles coated with such compositions. The new composition reduces the potential for loss of gloss when films or dried coated layers of the composition are stretched in thermoforming procedures and bonded to a substrate.